Broadcasting public warning messages over N3GPP access node of a non-3GPP network

ABSTRACT

The present invention provides a method of enabling a provision of public warning system, PWS, messages to a user equipment, UE, device via a non-3GPP radio network, the method comprising establishing an internet protocol security, IPSec, tunnel connection from the UE device to a non-3GPP interworking function, N3IWF, via a non-3GPP, N3GPP, radio access technology, requesting from a first core network, CN, entity a provision of public warning system, PWS, messages; and providing the first CN entity with information about a location of the UE device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is the United States national phase of International PatentApplication No. PCT/EP2019/071295, filed Aug. 8, 2019, which claimspriority to EP 18188487.5 filed Aug. 10, 2018, the entire contents ofeach of which are hereby incorporated by reference herein.

FIELD OF THE DISCLOSURE

The present invention relates to a mechanism for distributing publicwarning messages when a user equipment device is attached to a non-3GPPnetwork.

BACKGROUND

A user equipment (UE) device in general accesses the 3GPP core network(CN) through an access network that may be a radio access network (RAN).If the radio access network is defined by 3GPP, e.g. the newly defined5G radio access network, the access network provides a connection to anauthentication and mobility function (AMF). The AMF may be presentmultiple times in a single CN. An AMF is usually selected for a UE atregistration of a UE in the network and only one AMF is responsible fora single UE. The AMF, as all elements of the CN, can communicate toother CN elements through a routing infrastructure. The AMF for exampleconnects to the universal data management (UDM) to authenticate a UE atregistration, to receive information about subscribed services and toget security credentials used for communication with the UE.

A UE, when entering a cellular mobile network, selects a cell, e.g. thestrongest cell, and acquires information about the cell and theaccessible CNs from system information broadcast. If the selected cellis the most suitable, the UE sets up a connection to the respective basestation and connects from there to a selected AMF to requestregistration at the CN. The cells of a CN are grouped in tracking areas(TAs) and the UE device requests registration in the TA of the selectedcell. While registered, the CN always knows the TA or at least aconfigured list of TAs in which the UE resides so that the CN canconnect to the UE. If the UE is in connected mode, the CN can use theestablished connection between UE and AMF to connect, i.e. the AMF knowsthe serving RAN node (base station, eNodeB, eNB). If the UE is in idlemode, the CN can request the RAN to page the UE in all cells belongingto the TA or list of TAs in which the UE is currently registered. If theUE in idle mode changes to a cell with a TA not in the list ofconfigured TAs, the UE requests re-registration to inform the CN aboutthe new TA and request a new list of registered TAs.

If at any time the system information of a cell changes, the cellbroadcasts a paging message to inform all UEs currently residing in thecell about the change. The UE can then re-read the parts of the systeminformation that has changed. This mechanism releases the UEs from thenecessity to permanently monitor the system information to ensure theinformation used in the UE is up to date. Thus, UEs in idle mode canread the system information of a cell once when the cell is entered.After that, the UE listens to paging messages informing about systeminformation change or attempts of the CN to setup a connection to theUE, e.g. in case of a pending mobile terminated call or pending downlinkdata.

After authentication between UE and AMF for which AMF communicates withthe UDM, the UE is registered, and it can request services. If datadelivery to a data network (DN) should take place, e.g. to the internet,the UE requests setup of an appropriate connection, a so-called PDUsession, from the (R)AN to one or more User Plane functions (UPF) andfrom there to the data network. The appropriate context setup in theUPFs as well as the allocation of network resources is done by a SessionManagement Function (SMF). The SMF is selected by the AMF according tothe subscriber data, the data network to be contacted and currentnetwork load. A network exposure function (NEF) is responsible forexchange of data between the operator network (PLMN) and entitiesoutside that network. The NEF for example can provide subscriber ordevice specific information (reachability, available QoS, addresses) toservers outside the PLMN or it can provide information from outsideservers to CN entities.

Cellular mobile networks in general consist of access networks and acore network as described above. The access networks provide mainlycellular radio access to mobile device, e.g. via GSM, UMTS or LTE.Additional access networks may provide access via short range radioaccess, e.g. WLAN, or fixed or satellite access to mobile or fixeddevices. The access networks usually provide the complete functionalityto setup, control and maintain radio connections to devices.

The core network provides mechanisms that are not access specific, e.g.authentication, authorization and accounting (AAA) of devices and/orsubscribers, mobility between access networks and routing between theaccess networks and external data networks.

3GPP defines various access networks to access the 3GPP core network,e.g. GSM, UMTS, HSPA, LTE, LTE-A and in near future a 5G access network.These networks are developed to work specifically under control of the3GPP core network. The respective base stations support the securitymechanisms of the core network and they are setup and maintained by theoperator of the core network or a trusted third party. As a result, the3GPP access network can be trusted by the core network.

In addition, the 3GPP core network is setup to support access networksthat may not be setup and maintained by any trusted operator, they mayalso reside outside the operator's domain. These access technologies arecollectively named Non-3GPP access (N3GPP) and they may be so calleduntrusted N3GPP access if there is no trust relationship between thecore network and the access network.

FIG. 1 shows network elements that provide the UE with access to a CNvia 3GPP access technologies ((R)AN) and in addition the UE connected tothe CN via a non-3GPP access (N3GPP access, e.g. WLAN). The WLAN is anuntrusted node, therefore the WLAN itself connects to a non-3GPPinterworking function (N3IWF) that may accumulate multiple untrustednon-3GPP access networks (only one is shown in FIG. 1). The N3IWF is adevice that is maintained by the operator and is therefore trusted.

The non-3GPP access to a 5G core network requires the followingfunctionality to be performed to access the core network from a UE viauntrusted N3GPP access, e.g. WLAN:

-   -   The UE acquires IP-connectivity from the WLAN access point and        performs a selection of an N3IWF.    -   After that the UE establishes a security association with the        selected N3IWF using pre-shared secrets from the UICC of the UE.        The N3IWF selects an appropriate AMF, asks to authenticate the        UE or its respective subscriber and receives security        credentials. These credentials are the counterpart of those        generated by the UICC and build the base for the security        association with the UE. The UE and N3IWF setup an internet        protocol security (IPsec) tunnel so that the UE can securely        communicate with the N3IWF over the untrusted WLAN.    -   For setup of the IPsec tunnel, the N3IWF allocated to the UE a        second IP address from a N3IWF-local address space, the inner        IP-address. Also, the UE is provided with a destination IP        address from the same address space to which the UE addresses        control messages to the CN, i.e. to its AMF, the so called        NAS_IP_ADDRESS. The N3IWF uses the NAS_IP_ADDRESS as source and        the inner IP-address of the UE as destination for NAS signaling        over the IPSec tunnel.    -   Once the IPsec tunnel between UE and N3IWF and the interface        between N3IWF and the AMF are securely setup, the UE has a route        that constitutes its logical connection to the AMF.

The UE may now request to setup connections to a data network (DN) viauser plane functions (UPFs) over the untrusted WLAN. For that purpose,PDU sessions are setup via WLAN and N3IWFs and for the first and allsubsequent such PDU sessions the UE is provided with a seconddestination IP address from a N3IWF-local address space that the UE usesto address user data.

UE devices can use any N3GPP access that provides connectivity to theN3IWF of an accessible operator network (PLMN) to connect to thenetwork. Typical examples are private or public WLAN hot-spots providingpublic internet access. The UE can access the internet and via internetthe N3IWF and can thus setup a secure connection to the CN.

One result of the flexibility of N3GPP access is that the CN is notaware of the location of the UE or the N3GPP access node, e.g. the WLANaccess point. A UE accessing the CN may be at its home locationconnected to the user's private WLAN access point or at a hotel hot spotin another country. The UE device may in parallel be connected to a CNvia 3GPP access, i.e. the CN of the same PLMN as with the N3GPP or of adifferent PLMN.

As wireless, e.g. WLAN, access points are not under control of the PLMNoperator, they do not have a fixed location and they do not provide atracking area (TA) or cell ID information to a connected UE devicepointing at a location. Therefore, a 5G CN allocates a single TA to allN3GPP access networks. This TA allows distinction from 3GPP networks,but it does not provide any meaningful device location information.

While there are means to derive a device's location from its globallyroutable IP address, these means are neither trustworthy nor accurate.They usually lead to the location of the internet access point of theinternet service provider (ISP) instead of the device's location due tonetwork address translation performed in the ISP network.

3GPP specified a feature for public warning systems (PWS) providing theframework for several regional warning systems. PWS includes support ofJapan's earthquake and tsunami warning system (ETWS), the United States'commercial mobile alert system (CMAS) and Europe's EU-alert. A warningnotification provider outside the operator CN provides a warning messageand a notification area to the CN. The message is currently limited insize (90 or 316 characters) and it typically comprises the eventdescription, alert category, area affected, recommended action,expiration time and sending agency.

From the notification area a list of TAs and/or cells (cell IDs) isderived in which the warning messages need to be distributed. Thetransport of the messages uses broadcast mechanisms of the respectivecell. In 2G and 3G system the cell broadcast feature is used fortransport, in LTE systems a specific similar distribution mechanism isused based on an unacknowledged broadcast to all UEs capable ofreceiving the respective broadcast messages.

In LTE alert messages are transported in system information broadcastedin every cell. UEs are informed about new alert messages via pagingmessages similar to the system information change notification describedearlier in this document. UEs camping on a cell listen to paging for CNrequests to connect to the network, for system information changenotifications and for alert messages according to their individualpaging cycle. Roaming users and UEs must be supported by operators forPWS.

An alert category is specified globally to ensure a unique and definedmobile device behaviour. Users may be able to opt out of an alertcategory manually depending on device implementation and localregulation. For example, the CMAS “presidential alert” is not selectablewhile CMAS “extreme alerts with severity of extreme, urgency ofImmediate, and certainty of observed” is selectable. Alerts received bya UE device have to be brought to the user's attention immediately, i.e.shown on the display, while they must not break ongoing audio or videoconversations.

There are known warning message provisioning systems based on serversand over the top applications running on a mobile device. Warningmessages are received from warning notification providers and deliveredfrom the server on a dedicated, i.e. server to each device,IP-connection to every device that registered with one or more areas ofinterest comprising the notification area. These applications usuallyuse push notification mechanisms of the mobile device's ecosystem toalert the device. The application may inform the user according to thedevice's current state and according to the application settings and thestate of the device's MMI

US 2014/0273909 describes a method that prevents a UE device fromswitching from a network supporting delivery of public warning system(PWS) alert messages, e.g. a cellular mobile network, to a networkingnot supporting PWS message delivery, e.g. a N3GPP network, for apre-defined time after a PWS message has been received. The methodallows reception of further PWS alert messages expected to follow thefirst message by not switching to the N3GPP network or alternativelycommunicating with the N3GPP network while keeping a connection to thecellular network to receive PWS messages.

The described methods solve some deficiencies of prior-art by preventinga network connection to a N3GPP while the present invention enablesN3GPP networks to support the required service.

EP 1 798 898 A1 describes a method of selecting a radio access pointfrom a plurality of access points which may support different radiotechnologies such as WLAN and UMTS. A control entity on the network sidecan decide which of the plurality of access points should be used fortransmissions to a UE.

The public warning system (PWS) of 3GPP allows secure warning of usersof supporting devices in a PLMN, even devices that do not have an activeregistration to or a subscription with the PLMN. However, PWS messagesdo not work via N3GPP access technologies. Neither the broadcastmechanisms to efficiently deliver warning messages nor the locationmechanisms to provide alert messages at the correct notification areaare available.

However, the growing use of public hot spots and their use for access toa 3GPP network results in the demand to provide PWS over N3GPP access,especially over WLAN.

OTT applications provide a warning mechanism usable via public hotspotsand WLAN, but the usage is voluntary, not regulatable and requires auser to install and maintain an application on his/her device. Also, themechanisms only work on smart devices that can run such applicationswhile other types of UE device like simple phones, machines and sensorsare out of scope for such features.

As a result, there is missing a PWS usable over N3GPP access butcontrolled by an operator network and usable by a broad variety ofmobile devices.

US 2017/0289883 A1 describes a technique for handing over an establishedemergency services session from a cellular 3GPP wireless access networkto a non-3GPP wireless access network. The document is silent regardingthe transmission of PWS messages which would not require theestablishment of an emergency services session and indeed, theestablishment of an emergency services session in order to transmit suchPWS messages would be counterproductive.

GENERAL DESCRIPTION

Throughout this invention the terms core network functions and corenetwork entities will be used basically as a synonym. The term corenetwork function reflects the new language of the 5G standard,referencing functions that can be executed by a variety of actualentities of the network. Core network functions can for example beexecuted by server providing a virtual machine virtualizing networkentities for authentication and registration, for subscriber data baseaccess or broadcast delivery management. The term core network entity isused in former standards where the main functions like the onesmentioned above could be clearly associated to an entity, e.g. theMobility Management Entity. Throughout this invention, the terms areused exchangeable as they refer to functions provided by any physicalentity of the core network.

The present invention provides a method of enabling a provision ofpublic warning system, PWS, messages to a user equipment, UE, device viaa non-3GPP radio network, the method comprising establishing an internetprotocol security, IPSec, tunnel connection from the UE device to anon-3GPP interworking function, N3IWF, via a non-3GPP, N3GPP, radioaccess technology, requesting from a first core network, CN, entity aprovision of public warning system, PWS, messages; and providing thefirst CN entity with information about a location of the UE device.

A UE device may access a CN of a first PLMN via N3GPP access and aN3IWF, the UE device, having setup an IPSec tunnel to the N3IWF,requests from a CN entity delivery via the N3GPP access of alertmessages (such as warning messages or notifications about pendingwarning messages) provided by a warning notification provider, and theUE device informs the CN entity about its location in the form ofinforming about a cell ID and/or TA of a cell from which the UE devicereceived signals via a 3GPP access, or informing about a geo-position ofthe UE device, or subscribing with the CN entity to a group to whichalert messages are provided by the CN entity based on a notificationarea relating to the group, or subscribing with the CN entity to a groupto which alert messages are provided by the CN entity and the CN entitydetermining the UE device location from information received while theUE connects to the CN entity (e.g. IP-address).

The CN entity may be the N3IWF, the N3IWF using mechanisms of sourcespecific IP multicast (SSM) to deliver alert messages, with the N3IWFtransmitting alert messages via the IPSec tunnel to the UE device, thealert messages addressed to a multicast address specific for alertmessages and the alert messages having a source address relating to anarea comprising the notification area of the alert message, and the UEin that case subscribing with the N3IWF to a multicast (MC) channel(channel=MC source and destination address) specific for alert messagesfor an area comprising the location of the UE device.

Alternatively, the N3IWF may use mechanisms of any source IP multicast(ASM) to deliver alert messages, the N3IWF transmitting alert messagesvia the IPSec tunnel to the UE device, the alert messages addressed to amulticast address specific for alert messages for an area comprising thenotification area of the alert message, and the UE in that casesubscribing with the N3IWF to a multicast group (group=MC destinationaddress) specific for alert messages for an area comprising the locationof the UE device.

The N3IWF may subscribe at another CN entity (NEF) to a service (of thatentity) for delivery of alert messages relevant for the position of thatUE if it is not yet subscribed. In other words: The N3IWF may subscribeat another CN entity to a service (of that entity) for delivery of alertmessages relevant for the position of at least one UEs served by theN3IWF.

The CN entity may be an AMF, the AMF subscribing the UE device at theN3IWF to a multicast (MC) channel or a multicast group specific foralert messages for an area comprising the location of the UE device, andthe AMF also subscribing the N3IWF at a CN entity (NEF) to the same MCchannel or group if it is not already subscribed, or the AMF subscribingthe N3IWF at a CN entity (NEF) to a service for delivery of alertmessages corresponding to the MC channel or group (if it is not alreadysubscribed), and the AMF optionally storing the association betweenN3IWF and/or the UE device and the PWS service and relevant notificationarea or location of the UE device (note: the storage is not preferredbut an option, see embodiments).

The AMF may inform the UE device about one or more MC groups or MCchannels the UE device should receive (or should listen to) from theN3IWF in order to receive the requested alert messages, and a CN entity(NEF) may deliver alert messages relevant for a specific location to theN3IWF if at least one UE device indicated interest in the PWS service ofthe specific location. A single alert message (potentially in a fewrepetitions) is transmitted to the N3IWF for all UE devices connectedvia the N3IWF (i.e. in a multicast manner), and the N3IWF delivers alertmessages to UE devices subscribed to the group or channel thatcorresponds to the respective (notification area of the) alert message,the messages transmitted by the N3IWF to the UE device addressed to thegroup and delivered point to point through the secure tunnel establishedbetween UE and the N3IWF.

The CN entity may be a new entity dedicated to PWS or existing CNfunctions are extended to include PWS functionality, althoughimplementations of new PWS functions in N3IWF or AMF are beneficial itis not excluded to implement new PWS functions in either a new CN entityor extend an existing entity other than N3IWF or AMF.

Messages corresponding to the messages in sections above have to beexchanged between the PWS entity and N3IWF or AMF in any combination.

The CN entity (N3IWF or AMF) preferably informs the UE device duringregistration over a N3GPP access whether PWS is supported over the N3GPPaccess and whether PWS for an area is supported that comprises thelocation of the UE device. The UE device receives broadcast informationin a 3GPP access network to receive PWS alert message in case PWS is notsupported over the N3GPP access or PWS is not supported over N3GPPaccess for any area comprising the UE device location.

A UE may access a CN via N3GPP access and N3IWF, the UE informing theN3IWF about interest/capability to receive PWS alert message via IGMP,i.e. subscription to MC group or MC channel relevant for warning alertsat the location of the UE device, or the location is explicitly providedby the UE device to the N3IWF indicating a geo position, or anIP-address (with which the UE device is visible from N3IWF), or the UEdevice informs the N3IWF about a PLMN ID, the mobile country codethereof, and/or a TA and/or a cell ID received via a 3GPP accessnetwork, e.g. by providing the information explicitly or by subscribingto a group that is specific for an area comprising the country, thePLMN, the TA and/or the cell ID.

Alternatively, the UE may inform an AMF (e.g. during registration) aboutinterest/capability to receive PWS alert message, the UE informing theAMF about its locations in form of a geo position or PLMN, country, TAor cell ID, the position, PLMN, TA or cell ID may point to a locationoutside the general coverage area of the PLMN of the AMF, the AMFsubscribing the UE at the N3IWF to one or more MC groups or channelsrelevant for warning alerts at the location of the UE device.

The location of the UE device may be in the general coverage area of thesecond PLMN, i.e. the PLMN territory, but out of 3GPP access coverageand connected to the first PLMN via N3GPP access, e.g. in a cellar orbigger house or in a white spot of the second PLMN. An alert messagereceived by the UE device comprising information about the notificationarea of the alert and the UE determining based on that information andits own location whether the alert message is to be processed or not,e.g. whether the user of the UE device is to be alerted.

The UE may receive from the N3IWF or an AMF information whether PWS issupported via N3IWF in the CN or whether PWS is supported via N3IWF foran area comprising the location of the UE device and listen to broadcastof alert messages in a 3GPP access network if PWS is not supported inthe CN.

The UE device if PWS is not supported in the CN may de-register from theAMF in order to attach to a PLMN different from the PLMN of the AMF. Afirst PLMN (e.g. home) receiving from a UE device via a N3IWF a requestfor delivery of alert messages relevant for a notification areacomprising the location the UE device, the location of the UE devicebeing in the general coverage area of a second PLMN (e.g. visited) thatdoes not geographically overlap with the first PLMN, and the first PLMNtransmitting to the second PLMN a request for delivery of respectivealert messages, the request comprising location information relating thenotification area of the requested alert messages, and the first PLMNreceiving an acknowledgement of the request informing about the secondPLMN forwarding the requesting alert message to the first PLMN, and thefirst PLMN acknowledging to the UE device the delivery of the requestedalert messages (if such alert message are received).

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be described, by way ofexample only, with reference to the accompanying drawings in which:

FIG. 1 is a schematic illustration of a simplified 5G core network;

FIG. 2 is a simplified CN architecture in a roaming scenario;

FIG. 3 is a message sequence chart for the establishment of PWSmessaging;

FIG. 4 is a further message sequence chart of a second embodiment, and

FIG. 5 is a still further message sequence chart of a third embodiment.

DETAILED DESCRIPTION OF THE DRAWINGS

The general 5G core network architecture serving 3GPP access and N3GPPaccess for a UE has been described above.

FIG. 2 shows in addition a simplified CN architecture in the roamingcase, i.e. in the case where a subscriber accesses a CN that is not hishome PLMN. The UE registers at the AMF in the visited network similar towhat is described above, but the AMF contacts the home network forauthentication. The UDM and AUSF in the home network authenticate the UEand create a security context which is transferred to the AMF in thevisited network.

According to the new CN architecture of 5G, the UE may simultaneously toaccessing a visited PLMN via 3GPP access, access the home PLMN viaN3GPP, e.g. via WLAN over the internet. The N3GPP access is thenprovided via an N3IWF of the home PLMN and a second registration at anAMF in the home PLMN takes place.

The first embodiment is based on a general architecture according toFIG. 2, i.e. a UE is assumed to reside in a location where it cannotreach its home PLMN via 3GPP access. The UE may be in the generalcoverage are of a visited PLMN, but the UE is not registered to thevisited PLMN. FIG. 2 shows the connection to the RAN and the visitedPLMN in dashed lines because while a registration at the visited PLMN isassumed to be not available, the UE may in some embodiments receiveinformation from the visited network.

A first embodiment is shown as a message sequence chart in FIG. 3. TheUE first connects, e.g. via a WLAN, to an untrusted N3GPP access networkand obtains a local IP address. The WLAN provides access to a wide areanetwork, e.g. the internet, and the UE connects to a N3IWF of its homePLMN. It establishes a Security Association with the N3IWF so that anIPSec tunnel is further on used to exchange data securely between UE andthe N3IWF. The UE receives from the N3IWF an inner IP address and the IPaddress to be used for addressing CN signaling messages, i.e. messagesto and from the AMF. The UE registers at a selected AMF in the home PLMNwhich may include authentication via an AUSF and/or the UDM in the HomePLMN.

According to one aspect of the current invention, the UE also receivesfrom the N3IWF an IP address for addressing messages with regard to PWS,the PWS_IP_ADDRESS. The UE stores that address and during or afterregistration with the PLMN, the UE subscribes to PWS events at theN3IWF. The messages for subscription may be addressed to thePWS_IP_ADDRESS so that they can be clearly distinguished from NASmessages or user data in the N3IWK. The subscription may be performedusing the internet group management protocol (IGMP) as described in IETFRFC 3376. Alternatively, any other message framework and format may beused to inform the N3IWF that the UE requests delivery of PWS alertmessages via an IPSec tunnel associated with the UE.

In case IGMP is used, the subscription message may have the format of anIGMP state change report. The message contains filter information aboutwhich alert messages are relevant for the UE device, i.e. an alert levelor alert priority and information relating to the Notification Arearelevant for the UE. As filter information the multicast group to whichthe UE subscribes may be used so that there is one multicast group, i.e.one multicast destination IP address, for each notification area thatthe UE can subscribe to. Alternatively, the source specific multicast isused and there is one multicast channel for each notification area, i.e.one IP multicast source and destination IP address pair.

It should be noted that the filter information provided to the N3IWF maynot totally resolve the notification area of interest for the UE. It maybe foreseen that the UE subscribes to alert messages relevant for alarge area, e.g. the country in which the UE resides, and alert messagesthat are received by the UE are further filtered for local relevanceafter reception.

One example for filter information based on multicast groups is onegroup per country of relevance, another example would be one group perstate for alert areas within the home PLMN (assuming a federal state)and one group per country for countries outside the home PLMN.

One example for filter information based on multicast channels is onemulticast destination address per country and one multicast sourceaddress per region within the country. Another example is one multicastdestination address for the PWS service as a whole and one multicastsource address per country.

In this embodiment it is assumed the UE has the mapping betweenlocations or alert areas and filter information stored. The informationmay be received before the describes procedure started, e.g. through thehome PLMN while 3GPP connected, or it may be stored on the SIM card orobtained through the internet.

According to another aspect of this invention, the N3IWF subscribes atan entity of its PLMN to alert messages the UE subscribed to if it isnot already subscribed, e.g. due to another UE's request for suchmessages in the past. The entity to which the N3IWF subscribes can beany entity of the CN, e.g. an AMF or the UDM. But according to thecurrent network architecture, the network exposure function (NEF) hasthe general functionality to expose information like capabilities andevents to other network functions. The NEF can also communicate withauthenticated entities outside the PLMN to provide information receivedwithin the CN or to receive information from outside entities andprovide the information within the CN.

According to another aspect of this invention, the NEF of the home PLMNsubscribes at the NEF of a visited PLMN for alert messages relevant forthe general coverage area of the visited PLMN. This functionality of afirst PLMN subscribing at a second PLMN to alert messages relating tothe second PLMN's 3GPP access network coverage area is yet unknown. Itis of cause only executed if the first PLMN is not already subscribed tothe alert messages. This optionality is indicated in FIG. 3 by dashedlines.

This aspect can similarly be achieved by the NEF of the first PLMNsubscribing directly at an entity of a warning notification provider,e.g. operated by the authorities of the respective country. Themechanism is the same as the subscription at the second PLMN, only theentity will not be a CN entity like the NEF.

The subscription to alert messages between N3IWF and NEF and between twoNEFs of different PLMNs can use the same or different protocols as theUE subscribing at the N3IWF.

Now, at any time later (indicated in FIG. 3 by a dashed horizontalline), an alert message may be provided by a notification authority tothe second PLMN. The NEF of the second PLMN notifies the first PLMNabout alerts the first PLMN is subscribed to. It provides thenotification messages together with location information comprising thenotification area which may be provided in a much finer granularity thandefined by the subscription options. For example, if the subscriptionwas related to alert message of California, USA, the notification areain an alert message may relate to Union Square, San Francisco, USA.

The NEF in the first PLMN may thus filter the messages for relevance andit forwards the messages to all N3IWFs which subscribed to the messages.The N3IWK may filter the messages again based on location and relevanceinformation and forward the message as IP multicast message tosubscribed UEs, i.e. addressed to the destination address of thesubscribed to multicast group and sourced from either the source addresssubscribed to or the PWS_IP_ADDRESS. The multicast alert messages are,despite the fact they have been transmitted to the N3IWF as multicastand they are addressed as multicast, transmitted between N3IWF and theUE (and potentially other UEs receiving the same messages) individuallythrough the IPSec tunnel to the UE.

The UE may then finally filter the messages based on the NotificationArea provided with the message and a known location of the UE. If themessage passes the filter, i.e. the message is relevant for the UE orthe user, an alert is initiated. In case the UE is a user device with anMMI, an alert is provided to warn the user. In other cases, the alertmay result in appropriate action taken by a machine device.

A second embodiment is shown in FIG. 4. It may start with an optionalstep shown in the figure as dashed line and separated with dashedhorizontal line to emphasize that the optional step may occur at anytime before the procedure starts. The optional step assumes a UE in thecoverage area of a first PLMN to which it may or may not be registeredand which may be a visited or home PLMN. The UE receives in the firstPLMN broadcast information that bear location information, e.g. in theform of a tracking area or a cell ID of a cell that broadcasts theinformation. Alternatively, the cell broadcasts a PWS notification areaidentification which is relevant for the cell. The location informationis stored by the UE.

Now, the UE connects to a local N3GPP network and from there to a N3IWFof a second PLMN. The second PLMN may be identical to the first PLMN orit may be a different PLMN. FIG. 4 distinguishes the two PLMN as“visited domain” for the first PLMN and “home domain” for the secondPLMN just to ease readability and to provide a typical embodiment.Nothing in this invention should restrict the two PLMN to exchange rolewith regard to “home” and “visited” or to be identical, both “home” orboth “visited”.

For registration of the UE at an AMF, which may be during or afterestablishment of a Security Association with the N3IWF, the UE transmitsa registration request message to the AMF. According to this invention,the registration request may comprise information indicating that the UEneeds to receive PWS alert messages from the PLMN via the N3GPP access.The reason may be that the UE lost connection to the first PLMN, e.g.because it changed location, or the link properties changed, or becauseof a preference for registration to the second PLMN, e.g. its home PLMN.In addition to the information requesting PWS alert message delivery,the UE provides location information so that the AMF or any other CNentity in the second PLMN can determine which messages are relevant forthe UE. In addition, the UE may provide a relevance or priority levelfor filtering alert message to the AMF for further determination.

The location information may be in the form of a tracking area (TA) orcell identity previously received over a 3GPP access network asdescribed as an optional step in this embodiment. The locationinformation may alternatively be a geo-position of the UE determined bythe UE through built-in means like a GPS receiver or determined by an RFfingerprint (WLAN beacons and cellular network signals) or anycombination thereof.

Now, according to an aspect of this invention, the AMF in the secondPLMN may subscribe the UE to the respective alert message deliveryservice at the N3IWF. As a reference, the AMF uses a UE identificationand the AMF provides the notification area or areas to which the UEneeds to be subscribed.

Now, if the N3IWF is not already subscribed to the respective messagedelivery at the respective notification provider of the PLMN, e.g. theNEF as in the first embodiment, it will subscribe to that service as aresult of the subscription of the UE to the alert message delivery. TheNEF of the second PLMN may then subscribe to the service of the firstPLMN that is selected based on the subscribed to notification area bythe N3IWF.

Alternatively, the N3IWF in the second PLMN may be subscribed to therespective service of the NEF by the AMF. That is, the AMF may be theentity that subscribes the UE at the N3IWF and the N3IWF at the NEF tothe service. This alternative may need the AMF or any other CN entity ofthe second PLMN to store the subscriptions of the N3IWF to alert messagedelivery services, e.g. to prevent redundant subscriptions.Alternatively, the system ensures redundant subscriptions of the N3IWFto the same service do not cause any problems.

Before, during or after (the latter shown in FIG. 4) the subscription ofthe N3IWF at the NEF, the N3IWF confirms the subscription of the UE tothe AMF and provides address information to the AMF which is to be usedby the UE to receive PWS alert messages from the N3IWF. As described inthe first embodiment, this address information may be a PWS_IP_ADDRESSused to address multicast messages form the N3IWF. The addressinformation may also be a pair of IP addresses that constitute amulticast channel. The address information may also be different from anIP address if other mechanisms for message delivery than IP multicastare used.

The AMF finally provide the address information back to the UE, e.g. ina Registration Accept message, and it confirms the subscription to thePWS alert service. The UE used the address information to receive, i.e.listen to alert messages from the N3IWF.

The PWS alert message delivery may be the same as in the firstembodiment, it is therefore omitted here.

A third embodiment is depicted in FIG. 5. It starts very similar to thesecond embodiment; a UE may have received location information earlierand the UE now connects to a local N3GPP access network and to a N3IWFof its home PLMN. It sends a registration request message including anindication that PWS alert messages need to be delivered to the UE viathe N3IWF and N3GPP access. The indication comprises locationinformation to identify messages relevant for the UE.

In contrast to the second embodiment, in the third embodiment it isassumed that the home PLMN does not support delivery of PWS alertmessages to the UE. The reason may be that alert messages are notavailable to the home PLMN for the location provided. For that case theAMF may check for availability of alert messages after receiving theregistration request message. Another reason may be that alert messagedelivery over N3GPP access is not supported by the home PLMN at all.

Regardless of the reason, the AMF may accept the registration of the UEbut will indicate the rejection of the request to deliver PWS alertmessages. According to this invention, as a result of the rejection, theUE will start to search for an appropriate 3GPP network, select a cellof that network and start listening to alert messages provided by thenetwork over 3GPP access. Optionally, the AMF during or afterregistration via N3GPP access may provide the UE with informationsupporting the UE in receiving PWS alert messages via 3GPP, e.g.scheduling information.

Optionally, the UE may de-register from the home PLMN, providing therejection of the PWS service as a reason, and request, after networksearch and cell selection, a connection to the selected cell probablywith a following registration request (not shown in FIG. 5).

The invention claimed is:
 1. A method of enabling a provision of publicwarning system (PWS) messages to a user equipment (UE) device via anon-3GPP radio network, the method comprising: establishing an internetprotocol security (IPSec) tunnel connection from the UE device to anon-3GPP interworking function (N3IWF) via a non-3GPP (N3GPP) radioaccess technology, requesting from a first core network (CN) entity theprovision of public warning system (PWS) messages; providing the firstCN entity with information about a location of the UE device;subscribing by the UE device with the first CN entity to a group towhich alert messages are provided by the first CN entity based on anotification area relating to the group, the notification areacomprising the location of the UE device, and receiving by the UE devicethe PWS messages having a source or a target address relating to an areacomprising the notification area of the alert message as a result ofsubscribing, by the UE device via the IPSec tunnel.
 2. The methodaccording to claim 1, wherein the information about the location of theUE device is provided by at least one of: a cell identification of acell from the UE device received via a 3GPP access; a tracking areaidentification the UE device received via the 3GPP access; ageographical position of the UE device obtained using signalstransmitted by satellite; and an internet protocol (IP) address.
 3. Themethod according to claim 1, wherein the N3IWF is provided by the firstCN entity and wherein the PWS messages are delivered by source specificIP multicast or any source IP multicast.
 4. The method according toclaim 1, wherein a network exposure function (NEF) of a home public landmobile network (PLMN) subscribes at an NEF of a PLMN having ageographical coverage including the location of the UE device.
 5. Themethod according to claim 1, wherein the first CN entity includes anauthentication and mobility function (AMF) and wherein the AMFsubscribes the UE device to one of a multicast channel and a multicastgroup specific for the PWS messages for the area including the locationof the UE device.
 6. The method according to claim 5, wherein the AMFsubscribes the N3IWF to a second CN entity for delivery of the PWSmessages to the UE device.
 7. The method according to claim 1, whereinthe first CN entity informs the UE device over the N3GPP radio accesstechnology whether PWS messaging is supported over the N3GPP radioaccess technology.
 8. A user equipment (UE) device adapted to receivepublic warning system (PWS) messages, the UE device being arranged toaccess a core network (CN) entity by means of an internet protocolsecurity (IPSec) tunnel connection from the UE device to a non-3GPPinterworking function (N3IWF) via a non-3GPP (N3GPP) radio accesstechnology, wherein the UE device is further arranged to inform a firstCN entity about a capability to receive PWS messaging wherein thecapability may optionally indicate a desire of a user of the UE deviceto receive the (PWS) messaging, the UE device being adapted: to providethe first CN entity with information about a location of the UE device;to subscribe the UE device with the first CN entity to a group to whichalert messages are provided by the first CN entity based on anotification area relating to the group, the notification areacomprising the location of the UE device, and to receive via the IPSectunnel PWS messages having a source or a target address relating to anarea comprising the notification area of the alert message as a resultof a subscription by the UE device to the group.
 9. The UE deviceaccording to claim 8, wherein the first CN entity includes the N3IWF.10. The UE device according to claim 8, wherein the first CN entityincludes an authentication and mobility function.
 11. The UE deviceaccording to claim 8, wherein the UE device is arranged to receiveconfirmation information confirming registration of the UE device to aPWS message delivery service from the core network.